This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-060187, filed Mar. 6, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an ultrasonic diagnosis apparatus generating an ultrasonic wave image based on harmonic components of ultrasonic waves.
When ultrasonic waves propagate through a system, the waveform is distorted by a nonlinear effect. By this, a harmonic component is generated. Also, when ultrasonic waves hit a microbubble (ultrasonic contrast agent), the microbubble oscillates nonlinearly and collapses. And, at this moment, the harmonic component is generated.
The mechanism of generating harmonic components is given approximately by an equation as the square of an amplitude of the fundamental wave component. Because of this, the harmonic component is generated effectively in a high sound pressure zone. Therefore, compared with basic wave imaging, harmonic imaging is affected less by side lobe and excellent in aerial resolution.
However, compared with basic wave imaging, harmonic imaging tends to make contrast nonuniform. The cause, as described above, is that harmonic components are generated very much at ultrasonic focal points with high sound pressures and their peripheral zones, and on the other hand, they are not generated much in zones far from the focal points. Also, another cause is that, because of attenuation, harmonic components are generated rather much in shallow zones far from focal points, and on the other hand, they are not generated much in deep zones.
It is an object of the present invention to generate an image with relatively uniform contrast between a near distance and a view field depth.
An ultrasonic diagnosis apparatus has an ultrasonic probe having a plurality of arrayed transducer elements, a transmitting beam former for generating driving signals for driving transducer elements, and a receiving beam former for generating receiving signals based on echo signals received by transducer elements. The transmitting beam former generates driving signals so that phases of ultrasonic waves generated from transducer elements are aligned at multiple focal points. An image processor extracts harmonic components from receiving signals of ultrasonic waves having multiple focal points, and generates ultrasonic image data based on the harmonic components.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.